/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.flink.table.planner.plan.`trait`

import org.apache.calcite.plan.RelTrait
import org.apache.calcite.rel.{RelCollation, RelCollations, RelFieldCollation}
import org.apache.calcite.util.mapping.Mappings

import scala.collection.JavaConversions._
import scala.collection.mutable

/** Utility for [[RelTrait]] */
object TraitUtil {

  /**
   * Apply collation based on the given mapping restrict. Returns RelCollations.EMPTY if there
   * exists collation fields which has no target values in the given mapping.
   *
   * @param collation
   *   collation which to apply mapping
   * @param mapping
   *   mapping columns to a target.
   * @return
   *   A new collation after apply collation based on the given mapping restrict. Returns
   *   RelCollations.EMPTY if there exists collation fields which has no target values in the given
   *   mapping.
   */
  def apply(collation: RelCollation, mapping: Mappings.TargetMapping): RelCollation = {
    val fieldCollations = collation.getFieldCollations
    if (fieldCollations.isEmpty) collation
    else {
      val newFieldCollations = mutable.ArrayBuffer[RelFieldCollation]()
      fieldCollations.foreach {
        fieldCollation =>
          try {
            val i = mapping.getTargetOpt(fieldCollation.getFieldIndex)
            if (i >= 0) newFieldCollations.add(fieldCollation.copy(i))
            else return RelCollations.EMPTY
          } catch {
            case _: IndexOutOfBoundsException => return RelCollations.EMPTY
          }
      }
      RelCollations.of(newFieldCollations: _*)
    }
  }

}
